CN117447354A - Schiff base ligand mononuclear cobalt complex, preparation method and application thereof - Google Patents

Schiff base ligand mononuclear cobalt complex, preparation method and application thereof Download PDF

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Publication number
CN117447354A
CN117447354A CN202311408008.7A CN202311408008A CN117447354A CN 117447354 A CN117447354 A CN 117447354A CN 202311408008 A CN202311408008 A CN 202311408008A CN 117447354 A CN117447354 A CN 117447354A
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reaction
schiff base
complex
methoxyaniline
vanillin
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Chinese (zh)
Inventor
刘冬成
苏东惠
苏超
陈自卢
胡焕成
韦方沙
黄祖冰
黄春照
廖彩珍
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Guangxi Normal University
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Guangxi Normal University
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C251/00—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton
    • C07C251/02—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups
    • C07C251/24—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups having carbon atoms of imino groups bound to carbon atoms of six-membered aromatic rings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/22—Organic complexes
    • B01J31/2204—Organic complexes the ligands containing oxygen or sulfur as complexing atoms
    • B01J31/2208—Oxygen, e.g. acetylacetonates
    • B01J31/2217—At least one oxygen and one nitrogen atom present as complexing atoms in an at least bidentate or bridging ligand
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/40—Carbon monoxide
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C249/00—Preparation of compounds containing nitrogen atoms doubly-bound to a carbon skeleton
    • C07C249/02—Preparation of compounds containing nitrogen atoms doubly-bound to a carbon skeleton of compounds containing imino groups
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
    • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
    • B01J2531/84—Metals of the iron group
    • B01J2531/845—Cobalt
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
    • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
    • C07B2200/13—Crystalline forms, e.g. polymorphs

Abstract

The invention relates to a metal coordination compound, in particular to a Schiff base ligand mononuclear cobalt complex, a preparation method and application thereof, wherein the preparation method of the mononuclear complex comprises the following steps: placing o-vanillin and p-methoxyaniline in methanol, heating and refluxing for reaction, and vacuum drying the obtained reactant after the reaction is completed to obtain yellow crystals, namely the o-vanillin condensed p-methoxyaniline mono-Schiff base ligand; o-vanillin condensed p-methoxyaniline mono-Schiff base ligand and Co (OAc) are taken 2 ·4H 2 O is placed in a solvent, the pH value of the system is regulated to be alkaline,and (3) reacting under the heating condition, cooling the reactant after the reaction, separating out crystals, and collecting the crystals to obtain the target product. The mononuclear complex can be used as a catalyst in photocatalytic carbon dioxide reduction reaction, and has high activity and high selectivity.

Description

Schiff base ligand mononuclear cobalt complex, preparation method and application thereof
Technical Field
The invention relates to a metal coordination compound, in particular to a Schiff base ligand mononuclear cobalt complex, a preparation method and application thereof.
Background
Photocatalytic reduction of carbon dioxide is an effective way to slow global warming and provide green fuels and chemical feedstocks. Artificial simulation of photosynthesis is an important strategy for researchers to develop and utilize renewable energy sources, and clean, pollution-free and renewable solar energy is used for converting the renewable energy sources into chemical energy, so that energy storage and conversion are realized. The photo-catalytic carbon dioxide reduction system is composed of components such as a photosensitizer PS, a sacrificial reducing agent SD, a catalyst CAT, a solvent and the like. The photocatalytic carbon dioxide reduction process is complex, the products are changeable, and the development of a catalyst with high activity, high selectivity, high stability and low cost is an important index for developing a high-efficiency photocatalytic carbon dioxide reduction system. The invention patent of publication No. CN113797970A discloses a catalyst metal iron complex with photocatalytic carbon dioxide reduction activity, which is specifically shown in the following formula (1). Polypyridine is used as an organic ligand, and metallic iron (Fe) ions are used as a catalytic center. The complex has good photophysical and photochemical properties, and is often used as a catalyst for photocatalytic carbon dioxide reduction research.
In summary, selecting a proper catalyst is critical to the whole catalytic reaction, and research and report on photocatalytic carbon dioxide reduction by taking a mononuclear cobalt complex synthesized by Schiff base ligand o-vanillin-p-methoxyaniline single Schiff base as the catalyst are not yet seen.
Disclosure of Invention
The invention aims at: in view of the above-mentioned problems, a mononuclear cobalt complex capable of being used as a catalyst in photocatalytic carbon dioxide reduction reaction and exhibiting high activity and high selectivity, and a preparation method and application thereof are provided.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the molecular formula of the mononuclear cobalt complex is C 30 H 28 CoN 2 O 6 The structural formula is shown as the following formula (I):
the mononuclear cobalt complex belongs to monoclinic system and C2/C space group, and the unit cell parameters are as follows: α＝90°，β＝91.728(4)°，γ＝90°；
the preparation method of the cobalt complex comprises the following steps:
placing o-vanillin and p-methoxyaniline in methanol according to a molar ratio of 1:1, heating and refluxing for reaction, and vacuum drying the obtained reactant after the reaction is completed to obtain yellow crystals, namely the o-vanillin condensed p-methoxyaniline mono-Schiff base ligand; thenThen taking o-vanillin condensed p-methoxyaniline mono-Schiff base ligand and Co (OAc) according to the mol ratio of 2:1 2 ·4H 2 Placing O in a solvent, regulating the pH value of the system to be alkaline, reacting under a heating condition, cooling reactants after the reaction, separating out crystals, and collecting the crystals to obtain a target product;
wherein the solvent is CH 3 OH and C 2 H 5 OH is combined according to the volume ratio of 1:1.
In the preparation method, the pH value of the system is adjusted to be alkaline by adopting an alkaline substance, wherein the alkaline substance can be a common choice in the prior art, and is preferably triethylamine. It is further preferable to adjust the pH of the system to 7.5 or more, and it is more preferable to adjust the pH of the system to 8 to 10.
In the preparation method, the mixed solution obtained after the pH value is regulated is usually placed in a container, vacuumized, sealed and then placed under the heating condition for reaction. The reaction is preferably carried out at a temperature of 50℃or higher, more preferably 80 to 90 ℃. When the reaction is carried out at 80-90 ℃, the reaction time is generally controlled to 24-36 hours. The reaction is usually carried out by using a thick-walled hard glass tube with one end closed to contain the mixture obtained after the pH adjustment.
The invention also comprises application of the cobalt complex in preparing a catalyst, in particular application of the cobalt complex as a catalyst in photocatalytic carbon dioxide reduction. In a specific application, the photocatalytic carbon dioxide reduction system comprises a photosensitizer, a catalyst, a sacrificial agent and a solvent, wherein the catalyst is the mononuclear cobalt complex, and the photosensitizer, the sacrificial agent and the solvent are selected as in the prior art, and the photosensitizer is preferably [ Ru (phen) 3 ](PF 6 ) 2 、[Ru(phen) 3 ]Cl 2 Or [ Ru (bpy) 3 ]Cl 2 More preferably [ Ru (phen) ] 3 ](PF 6 ) 2 The method comprises the steps of carrying out a first treatment on the surface of the The sacrificial agent is preferably Triethanolamine (TEOA) and/or Triethylamine (TEA); the solvent is preferably CH 3 CN and H 2 O is mixed with mixed solution or DMF and H according to the volume ratio of 4:1 2 The mixed solution of O mixed according to the volume ratio of 4:1 is more preferably CH 3 CN and H 2 O is mixed according to the volume ratio of 4:1The solution was mixed. In the photocatalytic system, the concentration of the photosensitizer is preferably 400 to 500. Mu. Mol/L, the concentration of the catalyst is preferably 0.05 to 1. Mu. Mol/L, and the concentration of the sacrificial agent is preferably 0.30 to 0.35mol/L.
The invention also provides a catalyst which contains the cobalt complex.
In summary, due to the adoption of the technical scheme, the invention has the following beneficial effects:
compared with the prior art, the invention synthesizes one mononuclear cobalt complex with novel structure by an in-situ method, and the test result of the applicant shows that when 1 mu M mononuclear cobalt complex is used as a catalyst, 6.29 mu mol of carbon monoxide is produced by catalyzing carbon dioxide reduction, the TON value of catalytic conversion is 1257, and the selectivity to carbon monoxide is as high as 90.1%. Catalytic conversion TON when the concentration of complex was reduced to 0.05. Mu.M CO The value reaches 4880, and the conversion frequency reaches 0.136s -1 The selectivity to product CO is as high as 99%. TON of the mononuclear cobalt complex CO And TOF values are larger than most of complex molecular catalysts reported at present, which shows that the mononuclear complex prepared by the invention as a homogeneous molecular catalyst shows high activity and high selectivity in carbon dioxide reduction and has good photocatalytic performance.
Drawings
FIG. 1 is an infrared spectrum of the final product obtained in example 1 of the present invention.
FIG. 2 is a crystal structure diagram of the final product obtained in example 1 of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples in order to more clearly illustrate the present invention.
Example 1
Placing o-vanillin (1.5213 g,0.01 mol) and p-methoxyaniline (0.9310 g,0.01 mol) into a 100mL round-bottom flask, adding methanol, refluxing at 80 ℃ for 3 hours, and after the reaction is completed, vacuum drying the obtained reactant to obtain yellow crystals, namely the o-vanillin p-methoxyaniline monoservisory alkali ligand; o-vanillin condensed p-methoxyaniline mono schiff base ligand (0) is taken.0454g,0.2 mmol) and Co (OAc) 2 ·4H 2 O (0.0237 g,0.1 mmol) in a thick-walled glass tube was added 2ml of CH 3 OH and C 2 H 5 Solvents of OH composition (CH 3 OH and C 2 H 5 OH volume ratio of 1:1), regulating pH value of the system to 8 with triethylamine (30 mu L), sealing under reduced pressure, placing in an oven at 80 ℃, reacting for 24 hours, taking out, slowly cooling until crystal precipitation is completed, precipitating crystals, and collecting to obtain yellow crystals, thus obtaining the target product.
Characterization of the product obtained in this example:
(1) Infrared spectrum, the spectrum of which is shown in figure 1.
IR(KBr，cm -1 )：3106(w),3042(w),2943(w),2835(w),2603(w),2450(w),1572(s),1518(m),1425(s),1341(s),1233(m),1183(s),1109(m),976(w),858(m),739(m),690(w),582(w),439(w)。
(2) Analysis of the crystal structure:
selecting black needle-shaped crystal with moderate size, placing on Bruker SMART CCD diffractometer, and adopting graphite monochromatizationThe rays were used for single crystal testing. The initial crystal structure of the product obtained in this example was all solved by SHELXL-97 direct method, the geometric hydrogenation was performed, and the non-hydrogen atomic coordinates and anisotropic thermal parameters were refined by SHELXL-97 by full matrix least squares method. The obtained crystallography and structure refinement data are shown in table 1, the chemical structure of the obtained black needle-shaped crystals is shown in fig. 2, and the obtained yellow crystals are determined to be target products of the invention.
TABLE 1 crystallographic data of mononuclear cobalt complexes according to the invention
Example 2
Example 1 was repeated, except that the reaction was modified at 50 ℃.
As a result, yellow crystals were obtained.
The product obtained in this example was subjected to high-resolution mass spectrometry, infrared analysis and single crystal diffraction analysis, and the yellow crystal obtained was confirmed to be the target product of the present invention.
Example 3
Example 1 was repeated, except that the reaction was modified at 90℃for 36h, and the pH of the system was adjusted to 9 or 10 with triethylamine.
As a result, yellow crystals were obtained.
And carrying out high-resolution mass spectrometry analysis, infrared analysis and single crystal diffraction analysis on the product obtained in the embodiment, and determining that the obtained yellow crystals are all target products of the invention.
Experimental example 1: the mononuclear cobalt complex is used as a homogeneous catalyst to carry out experiments on photocatalytic carbon dioxide reduction in an aqueous system.
(1) The materials used
The solvent is (CH) 3 CN/H 2 O4:1, v/v) mixed solution, the catalyst was a cobalt complex (hereinafter referred to as complex 1) prepared according to example 1 of the present invention, and the photosensitizer was [ Ru (phen) ] 3 ](PF 6 ) 2 The sacrificial agent is TEOA, and the LED lamp source (wavelength 450nm, light intensity 100mW cm) -2 An irradiation area of 0.8cm 2 ) 15mL of a quartz reactor, carbon dioxide gas, a rubber tube, an analytical balance, a stirrer and a gas chromatograph.
(2) Photocatalytic Experimental procedure
The photocatalysis experiment selects a quartz bottle with the volume of 15mL as a reaction vessel, and the catalysis system comprises: solvent 5mL (CH) 3 CN/H 2 O4:1, v/v) mixed solution, catalyst, photosensitizer and sacrificial agent. Sealing the mixture by using a rubber tube, introducing carbon dioxide or nitrogen for 15min, and sealing the mixture by using vacuum ester and a sealing rubber strip. Irradiation with LED lamp (λ=450 nm, intensity 100mw·cm at room temperature -2 Irradiation area 0.8cm 2 ). Photocatalytic reactionThe resulting gas product was detected by an Agilent 7820A or 8890A gas chromatograph using a TCD detector. And detecting the liquid phase product by using an ion chromatograph and a nuclear magnetic resonance spectrometer. Each group of photocatalytic reactions is measured at least three times in parallel, and then an average value is obtained so as to ensure the reliability and the repeatability of the data. The obtained results: at 1 mu M of mononuclear cobalt complex, 6.29 mu mol of carbon monoxide is produced by catalyzing reduction of carbon dioxide, the TON value of catalytic conversion is 1257, and the selectivity to carbon monoxide is as high as 90.1%.
Different parallel experiments (as shown in Table 2) were performed on the above method. As can be seen from Table 2, the photocatalytic effect of the cobalt complexes of the present invention on photocatalytic carbon dioxide reduction under aqueous and visible light conditions is significantly higher than most of the reported catalytic systems.
TABLE 2 photocatalytic carbon dioxide reduction experimental data for cobalt complexes as catalysts in accordance with the present invention
Reaction conditions: at a constant temperature of 25℃with an LED lamp having a wavelength of 450nm (intensity of 100 mW.cm -2 Irradiation area 0.8cm 2 ) The middle and lower part of the quartz tube was illuminated for 10 hours. Photosensitizer: [ Ru (phen) 3 ](PF 6 ) 2 Concentration was 0.4mM; sacrificial agent: TEOA, concentration 0.3M;5mL CH 3 CN/H 2 O (4:1, v/v) was used as the solvent of the reaction system. The average value is measured at least three times for each group of catalytic reactions, and the average standard deviation is less than 10%.
From the photocatalytic results, it can be seen that: the mononuclear cobalt complex synthesized by the invention is used as a homogeneous catalyst and has high activity and high selectivity in the reduction of visible light catalytic carbon dioxide in an aqueous system. When the concentration of the complex was reduced to 0.05. Mu.M (see Table 2), the catalytic conversion number TON was reduced CO The value reaches 4880, and the conversion frequency reaches 0.136s -1 The selectivity to product CO is as high as 99%. TON of the mononuclear cobalt complex CO And TOF values are greater than most of the complex molecular catalysts reported so far.
The foregoing description is directed to the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the invention, and all equivalent changes or modifications made under the technical spirit of the present invention should be construed to fall within the scope of the present invention.

Claims (9)

1. A Schiff base ligand mononuclear cobalt complex, characterized in that the cobalt complex has the chemical formula: c (C) 30 H 28 CoN 2 O 6 The structural formula is shown as follows:
2. the method for preparing a mononuclear complex according to claim 1, comprising the steps of:
placing o-vanillin and p-methoxyaniline in methanol according to a molar ratio of 1:1, heating and refluxing for reaction, and vacuum drying the obtained reactant after the reaction is completed to obtain yellow crystals, namely the o-vanillin condensed p-methoxyaniline mono-Schiff base ligand; o-vanillin condensed p-methoxyaniline mono-Schiff base ligand and Co (OAc) are taken according to a molar ratio of 2:1 2 ·4H 2 Placing O in a solvent, regulating the pH value of the system to be alkaline, reacting under a heating condition, cooling reactants after the reaction, separating out crystals, and collecting the crystals to obtain a target product;
wherein the solvent is CH 3 OH and C 2 H 5 OH is combined according to the volume ratio of 1:1.
3. The preparation method according to claim 2, wherein the pH of the system is adjusted to be 8-10.
4. The process according to claim 2, wherein the reaction is carried out at a temperature of at least 50 ℃.
5. The process according to claim 2, wherein the reaction is carried out at 80 to 90 ℃.
6. The process according to any one of claims 2 to 5, wherein the pH of the system is adjusted to alkaline with an alkaline substance.
7. Use of the complex of claim 1 for the preparation of a catalyst.
8. The use according to claim 7 as a catalyst in photocatalytic carbon dioxide reduction.
9. A catalyst comprising the complex of claim 1.
CN202311408008.7A 2023-10-27 2023-10-27 Schiff base ligand mononuclear cobalt complex, preparation method and application thereof Pending CN117447354A (en)

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